There is growing awareness of the need to measure plantar pressure for gait prediction and clinical applications. This is especially the case in the measurement of normal pressure and shear pressures. The purpose of this paper is to design a flexible tactile sensor array based on polyvinylidene fluoride (PVDF) piezoelectric film for plantar pressure measurement, which can simultaneously measure three-axis pressure, respectively, x-axis, y-axis, z-axis.
The sensor array consists of four PVDF piezoelectric films as sensor elements and two PDMS membranes as upper and lower substrates. The structure of the proposed sensor array is simulated through ANSYS software. The direction and the amplitude of plantar pressure are deduced from the four piezoelectric sensor elements with high sensitivity, which can generate related signals corresponding to the compressive and tensile stress. The performance of the sensor array is characterized through calibration experiments. And the preliminary plantar pressure measurement is also conducted to verify feasibility of the sensor array.
Average sensitivities calibrated from the experimental results are (14.33 ± 1.22) mV/N for the x-axis pressure, (32.27 ± 2.26) mV/N for the y-axis pressure and (30.17 ± 3.24) mV/N for the z-axis pressure. The plantar pressure measurement experiment indicates that the sensor array can simultaneously measure normal pressure and shear pressures, providing a basis for accurate analysis of plantar mechanical state.
The results obtained from measurement experiments can be used to monitor plantar pressure, predict gait and is expected to be useful in in modern robot technology and flexible electronic applications.
